For Postcards,I charge the following:
(UK, £1) (Europe, £1.50) (Rest of World, £2.25). This price is for any number of cards paid for together.
If you are not sure what to do, just wait. There's no need to contact me on this unless I haven't sent you a combined invoice within a couple of days.
I post to anywhere in the world, but prefer customers outside the UK to use paypal.
If you do need to contact me for any reason, always use ebay's messaging system and never email.